Thanks for the info guys, much appreciated! Current train of thought is to just put the notice in, and apply about 6-8 months out from my expected availability. If I end up in a hold pool, I'll try and find some other work to tide me over until a start date is offered.
Final related question, is Jet2 likely to be picky about how recent the last flight was? I've got the start of a plan to do some travelling for 2-4 months between RAF and starting, just wondering if that's a non-starters as I'll likely be out of a cockpit for 5 months before starting with an airline.